#include <sys/types.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <pthread.h>
#include <sys/time.h>

pthread_t t1;
pthread_t t2;
pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
int c;

void cancellation(void *nothing) {

  if (pthread_mutex_lock(&m)) 
  {
    printf("cancellation: lock error.\n");
    exit(1);
  }

  c++;

  if (pthread_mutex_unlock(&m)) 
  {
    printf("cancellation: unlock error.\n");
    exit(1);
  }

}

void *thread1(void *nothing) {
  pthread_cleanup_push(cancellation, NULL);

  while (1) 
  {
    usleep(10);
  }

  // never reached
  pthread_cleanup_pop(NULL);
  exit(5);
  return NULL;
}

void *thread2(void *nothing) {

  // wait until t1 is created
  pthread_mutex_lock(&m);
  pthread_mutex_unlock(&m);

  if (pthread_cancel(t1) != 0) 
  {
    printf("cancel error.\n");
    exit(1);
  }

  if (pthread_join(t1, NULL)) 
  {
    printf("join t1 error.\n");
    exit(1);
  }

  pthread_exit(NULL);
  return NULL;
}

int main(void) {

  int i = 0;
  struct timeval tv1, tv2, dt;

  printf("pid: %d\n", getpid());

  gettimeofday(&tv1, NULL);

  c=0;
  while (1) {

    if (pthread_mutex_lock(&m)) 
    {
      printf("lock error.\n");
      exit(1);
    }

    if ( pthread_create(&t1, NULL, thread1, NULL)
      || pthread_create(&t2, NULL, thread2, NULL)) 
    {
      printf("create error.\n");
      exit(1);
    }

    if (pthread_mutex_unlock(&m)) 
    {
      printf("unlock error.\n");
      exit(1);
    }

    if (pthread_join(t2, NULL)) 
    {
      printf("join t2 error.\n");
      exit(1);
    }

    if (i++ % 1000 == 0) 
    {
      gettimeofday(&tv2, NULL);
      timersub( &tv2, &tv1, &dt );
      printf("i=%d, c=%d, dt=%ld.%06ld\n", i, c, dt.tv_sec, dt.tv_usec);
      tv1 = tv2;
    }

  }

  return 0;
}